The conventional method of connecting the two longitudinal steel shapes is to weld the shortened beam materials b and b to face with each other, to a pair of longitudinal materials a and a, erected on the ground and then, connect the shortened beams b and b, with a long beam c. At the connected parts, the edge of the shortened beam piece b, cut at tight angles and the edge of the long beam c, are butt jointed together; then to the ribs on both sides of the butt jointed ends, the patch plates, d and d, and to the upper and lower flanges, the patch plates e and e, are fixed for connection. However, in this work it is necessary to lighten the connection with lots of bolts and nuts and, therefore, the work involves troubles and requires lengthly hours in addition to the bolts, nuts and patch plates.
Furthermore, the hole drilling has to be performed on the patch plates for numerous bolts to make the work highly uneconomical.
To make the situation still worse, until the tightening work with the bolts and nuts is completed the beam materials have to be constantly supported by the cranes or the like with dangerous probabilities for their dropping down. Thus, it bears a defect in that the work has to be progressed in an uneasy condition constantly.